1. Field of the Invention
The present invention generally concerns a wheel chocking system for securing motor vehicles on the decks of transporters as exemplified by railway cars. More particularly, the present invention concerns a low-profile, high strength, metallic chock construction for restraining and securing a vehicular wheel to a wheel support surface.
2. Discussion of the Prior Art
For many years, vehicular wheel-to-railcar securement means were defined by tie down chains which interconnected the vehicle body and the structure of the railcar and which were tightened to compress the suspension springs of the vehicle. More recently, increasing attention has been given to restraint schemes employing vehicular wheel chocks.
Early vehicular wheel chock constructions and chocking systems employed cast chock constructions consisting of lightweight polymeric or aluminum type materials as exemplified by those mechanisms disclosed and described in U.S. Pat. No. 4,875,813, issued to Moyer et al. and U.S. Pat. No. 5,316,421, issued to Bullock et al. At that time, rail industry standards called for vehicular wheel chocks adapted for releasable attachment to a prescribed mounting rail of hat shape in cross section extending lengthwise of the support deck and each of whose upright walls contains a uniform pattern of locking holes. Current industry mandates call for lower-profile wheel chock constructions in view of the recent trend in vehicular design toward vehicles with reduced clearance between the ground and their underbody, and toward reduced clearance between the vehicles wheels and the internal surfaces of the vehicular wheel wells.
The railroad industry has thus provided a clear instruction, namely, to establish a new generation of “low-profile” vehicular transport wheel chocks having a maximal side elevational height of about 4 inches (or about 10 cm) in order to ensure that the vehicular wheel chocking system and vehicular wheel chock construction would structurally cooperate with vehicles having these newly developing low clearance concerns.
Early vehicular wheel chock assemblies may be exemplified by the invention made the subject of U.S. Pat. No. 4,875,813 ('813 patent), issued to Moyer, et al. The '813 patent discloses a Wheel Chock for restraining motor vehicles during railway transport. The chock according to the '813 patent comprises a monolithic body defined by a synthetic plastic molding or an aluminum casting and is provided with a pair of locking pins and a latching mechanism for releasably securing it to a mounting rail fixed on a deck of the vehicle transporter. The chock also incorporates a reeling mechanism, including a pawl and ratchet locking device, for holding and tensioning an over-the-wheel safety harness.
U.S. Pat. No. 5,037,255 ('255 patent), and U.S. Pat. No. 5,316,421, both of which issued to Bullock et al., disclose certain relatively newer chocking systems. The '255 and '421 patents both describe a wheel chock quite similar to the Moyer chock for a motor vehicle, which chock is primarily constructed from a composite material and adapted to be selectively connected to a pair of rails fastened to the container floor. The flexible copolymer material of the chock body is said to be capable of withstanding loads incurred by vehicles restrained by the chocks, and which is constructed to be easily connected to and disconnected from the rails and be supported above the container floor to prevent damage to the floor.
The chock of the '421 patent is further said to be user friendly in that it can be maintained in a wheel-restraining position together with a wheel harness and removed from that position without the use of any tools. The wheel chock includes a torque tube for winding up a wheel harness strap to tighten the wheel harness on a vehicle wheel, a strap take-up device for quickly removing the slack in the strap, and a foot-operated actuating lever for rotating the torque tube and operating a pawl and ratchet mechanism controlling rotation of the torque tube.
The chock bodies shown and described in at least the Bullock patents, as well as perhaps the Moyer chock body, being made of plastic, would structurally requires a more robust steel plate in order to carry the vertical load imparted when a secured car tire tries to roll or slide away from it. Diagrams in the disclosure of Moyer suggest that the Moyer plastic body alone is designed to effectively resist all functional loads the chock might experience. However, the diagrams in the Bullock disclosure quietly admit that there is a ⅛″ thick metallic support plate coupling the main axis of the winch (designated with number 85 in FIGS. 2 and 3 of Bullock and elsewhere) to the pair of bolts also known as track pins (designated with number 43 in FIGS. 2 and 3 of Bullock).
A side by side comparison of FIG. 3 from the Moyer disclosures in U.S. Pat. No. 4,875,813 and FIGS. 2 and 3 from the Bullock et al. disclosures in U.S. Pat. No. 5,316,421 illustrate a key structural difference (i.e. a steel plate) between those two chock constructions although Bullock et al. are silent in their specification regarding the additional of a metallic structural plate to overcome the design defects of the Moyer et al. chock assembly.
Referencing Column No. 4, Line Nos. 7-11 of Moyer et al., the reader will note that the Moyer pins 36 and Moyer nuts 37 function to attach the (polymeric or aluminum cast) structural member or web 26 to the rail 32. Referencing Column No. 4, Line Nos. 13-28 of Bullock et al. the reader will note that Bullock pins 43 are mounted to the (polymeric) web 31 via nuts 45 and washers 46. Comparatively referencing FIG. 3 of Moyer et al. versus FIGS. 2 and 3 of Bullock et al., however, the reader will further detect a structural form present in Bullock et al. intermediate the web 31 and the head of pins 43. This structural form is a steel plate, introduced into Bullock et al. chock to enhance its strength and prevent structural fracturing during loading events.
The Moyer patent represents what is known within the rail shipping industry as the 1st generation of the Standard Car Truck Company's Copolymer chock. This chock quickly had performance problems in the field, often releasing itself from the railcar deck and allowing damage to the cargo. The response to Moyer chock was the addition of the metal support plate shown but not discussed in the Bullock et al. patent, and this latter version became known as the 2nd generation. Those with the “user friendly” enhancements detailed in Bullock became known as the 3rd generation.
Environmental extremes are well known to cause problems for the copolymer chock body's plastic material exemplified by Moyer and Bullock. Cold temperatures render the material brittle and subject to fracture during unloading operations, when conditions also require the breaking of ice that has adhered to the device during transport. Hot weather renders the material more flexible and soft, increasing the likelihood that the device may fail under loading during impact conditions such as those described above.
The focus on constructing a primary chock body from polymeric materials has clouded certain opportunities for further development in this field, particularly in view of the fact that attempts to improve upon the state of the art included the addition of metallic structural supports for strengthening the polymeric materials. The present response to the perceived need in the art involves addressing the complexity of the many walls and passages in the polymeric design, and designing a relatively more robust steel or metallic fabrication that is both cost effective and substantially similar in weight to the prior art polymeric chock designs.